Using Fiber Cable in IQ Networks

Fiber optic cable keeps becoming more popular as it increasingly becomes more cost effective and more widely understood. A common application for fiber with IQ is to extend the IQ Bus data loop on long runs between equipment rooms. The information below explains...

The Concept

Audio system installers are always looking for better ways of getting audio and data distributed around large facilities. One popular transmission medium is fiber optic cable. Fiber optic cable can be used to transmit almost any type of signal by converting the electrical signal to light, then back to electrical at the remote end. Fiber is already used extensively by telephone companies and is used in many large network applications. It works well at almost any signal frequency, can be used for very long distances, and provides total electrical isolation without the threat of interference. Fiber optic cable, though not used as extensively in the audio industry, can be a powerful tool when properly integrated in medium to large audio installations.

Applications

In an IQ Network, there are two very general applications for fiber optic cable. The first is transmission of audio from a central source to satellite amplifiers located in remote equipment rooms. The second is transmission of data for system control. Depending on various factors, fiber can be used for either or both, and in some cases audio and data can even travel over the same fiber strand.

Analog vs. Multiplexed Fiber

There are two basic types of fiber transceiver equipment. Analog transceivers convert one electrical signal into one light signal, then back again at the other end. Multiplexing transceivers can take multiple signals and transmit them simultaneously over the same fiber strand. This is done by digitally sampling lower frequency signals at a very high frequency and synchronizing them for transmission on a time-share basis. The same principles can be applied to wire, however the high efficiency and small size of fiber cable makes this a very economical method of getting large numbers of signal around a large facility.

Analog Transceivers

Analog fiber transceivers take a single signal and converts it to light, then back again at the remote end of the fiber strand. The most significant advantage of using analog transceivers in an audio application with IQ is cost and simplicity. This is particularly true when only the data of the IQ Bus data loop or RS-232 needs to be transmitted a long distance. There are many off the shelf fiber transceivers on the market for RS-232. The IQ Bus, however, is designed for normal operation on twisted pair wire as a 20 milli-amp current loop. When converted to fiber, special electronics are required at the transceiver for proper conversion. Crown is not a fiber optic manufacturer, however, Crown does work closely with fiber transceiver manufacturers. One company that does have an analog fiber transceiver designed specifically for the IQ Bus serial data loop is Fiber Options.

Multiplexing Transceivers

Where data and audio need to travel down the same fiber strand, it is necessary to multiplex multiple channels together. This can be done with a multiplexing transceiver. Multiplexes sample several audio and/or data channels and convert all the signals to high frequency digital information. At the remote end of the strand, a demultiplexer takes the synchronized data, divides the channels, and converts the signals back to their original form. Like analog transceivers, the multiplexers must also be able to receive and transmit the 20 milli-amp current loop information, thus requiring similar special electronics. B.E.C. Technologies, an Orlando, Florida, based company, manufactures such equipment. Multiplexing audio and data may be more expensive, however the total cost depends on the type and quantity of signals that need to be shipped around a facility.

Fiber Optic Cable

There are at least a dozen fiber transceiver companies in the U.S. alone. We have mentioned two by name due to their history of working with the IQ Network. There are probably twice as many manufacturers of fiber cable. The cable can come in various forms, with various specifications. For use with IQ, we strongly recommend that the cable you select be of high quality and durability.

Fiber Concerns

Fiber has advantages and disadvantages. If it were the perfect transmission medium, it would be far more widely used than it already is. Many of the advantages are described above. For short cable lengths fiber is often cost prohibitive. Tools used to terminate wire are general inexpensive and easy to obtain, whereas fiber tools are usually more expensive. Fiber terminations should only be made by trained professionals since very special care must be taken. If the tip of a wire breaks, removing a short length of sleeving usually takes care of it. If the tip of a fiber strand breaks, the end must be polished and processed and a new terminator must be installed. Also, fiber can splinter and be a serious health hazard if improperly handled.As it pertains to IQ, the biggest reason most people jump on fiber for transmission of the IQ Bus is to extend the length of the IQ Bus long distances, such as between remote equipment rooms. This is a valid reason to use fiber, but using fiber does not automatically imply that Crown IQ-RPT Repeaters are not still needed. Fiber transceivers, like the wire or loop components, can add degredation to the IQ Bus data signal. Fiber transceivers do not reconstruct the loop. Repeaters are often required in installations using fiber to make up for signal loss in the transceivers and remaining wiring.

Fiber Transceiver Manufacturers

As mentioned before, Fiber Options and B.E.C. Technologies are two companies that have transceivers available specially designed for the IQ Bus. For more information contact:

IQ Compatibility

The IQ Bus is defined as a carrier of IQ protocol on a serial data loop. Though it normally operates as a 20 milli-amp current loop, the definition leaves open the choice of mediums. Fiber optic cable is one alternative. The type of transmission media, be it twisted pair wire, fiber optic cable, or anything else, is without regard to the actual data information being communicated. It necessarily must meet the fundamental hardware requirements for interconnection with IQ Network hardware, however there are no compatibility issues to consider regarding the protocol itself.